The invention is based on an electromagnetically actuatable injection valve as defined hereinafter.
U.S. Pat. No. 3,646,914 discloses an electromagnetically actuatable injection valve for an internal combustion engine that has a tubular stroke adjustment sleeve, which is screwed into a bore of a valve end cap of a valve housing of the injection valve and serves both as a core and as a stop for a valve closing member that cooperates with a fixed valve seat. When the injection valve is open, an upstream face end of an armature that is firmly joined to the valve closing member rests on a face end of the stroke adjusting sleeve oriented toward the armature. Rotating the stroke adjusting sleeve makes it protrude more or less far into the injection valve, depending on the direction in which it is rotated. The stroke of the valve closing member can be adjusted in this way. The stroke of the valve closing member is shortened by turning the stroke adjusting sleeve inward. Conversely, the stroke is lengthened if the stroke adjusting sleeve is rotated farther out of the injection valve. By lengthening or shortening the valve closing member, the static injection quantity of the injection valve is increased or decreased, respectively.
The valve closing member is acted upon by a restoring spring, which is supported on a spring adjusting sleeve screwed into the stroke adjusting sleeve and prestresses the valve closing member in the direction of the valve seat. The magnetic force generated by the magnet coil in the excited state, which moves the armature in the direction of the magnet coil and lifts the valve closing member from the valve seat, acts counter to the force of a restoring spring. Turning the spring adjusting sleeve inward in the direction of the valve closing member increases the prestressing of the restoring spring, which lengthens the time that elapses until the injection valve is fully open. Varying the prestressing of the restoring spring adjusts the dynamic injection quantity injected during the opening or closing process. The static and dynamic injection quantity are adjusted independently of one another with the injection valve in the fully installed state.
If the injection valve is fully open, the upstream face end of the armature rests on the face end of the core toward the armature. In an ensuing closing motion, because of adhesion and residual magnetism, the armature sticks to the face end of the core, slightly delaying the onset of the closing motion. Because the closing motion of the valve closing member obeys the activation signals of an electronic control unit only with a delay, the composition of the fuel-air mixture is not optimal, which translates into increased emissions, inadequate engine power, and poor engine running properties.